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From: "Glen Todd" <>
Subject: RE: [DNA] Amazing article about genetics -- please help
Date: Sun, 14 May 2006 21:03:40 -0600
In-Reply-To: <32d.40d9fb6.31993945@aol.com>


> I'm not knowledgeable about the science of genetics, and I
> found this article that appears to come from a reliable
> source on the "Genealogy in St. Louis" > web site. Some of
> the content amazes me. For example, this Dr. Shoemaker

I'll leave a detailed analysis to others, but basically this guy is a poor
writer and a worse scientist. He doesn't even make an effort to make a
'case' for his statements.

> states that "it is no exaggeration to say that it is likely
> that every person of Northern European descent is a descendant of
> Charlemagne...".

This is possible to likely. For instance, I have according to my
genealogical database program a total of 20 purported genealogical direct
lines back to ol' Mangy Charlie, who, if the links are reasonably correct,
is my 34th great grandfather that many different ways. This sounds
impressive, but if you do the math, the mathematical total of any person's
number of ancestors 37 generations back (we're talking the latter 8th
century CE, after all) is considerably greater that than the total
population of the world at that point, so obviously in any area such as
Northern Europe there is going to be a LOT of convergence. Given the low
population mobility during the subsequent thousand years and the fact that a
number of important (and prolific) lines descended from Charlie the Mange,
the probability that most if not all people of Northern European descent can
trace at least one direct line to him approaches unity. Of course, that
could also be said for a great many other people alive at that time who are
less well documented than he.

This statement, in short, is an attention grabber but effectively
meaningless.

> He believes that on average all people alive today are as
> genetically similar as third cousins.

Again, a fancy statement, but meaningless. For instance, what does
'genetically similar' mean? All human beings ARE identical in the vast
majority of their genetic material. That's what makes us human beings and
not geckos or strawberry bushes. There are so very many genes, though,
that even a fraction of a percent's difference is more than enough to
produce the human variety that you can easily see by walking down any city
street.

In genealogical terms, your third cousins have a common ancestor with you at
around the time of the American Civil War. For me (and I'm fairly normal
in this respect) my third or closer cousins would be descendants of at least
one of only eight pairs of great-great-grandparents. If I could identify
and round up every single one of my living relatives that close or closer,
we could probably have a comfortable family reunion in the group picnic
shelter area down at Memorial Park. That's a LONG way from being the
entire population of the world.

This seems to be another place where he has played fast and loose with
definitions.

> It also appears that he believes we are all pretty inbred.

See my numbers earlier. We are. A person's mathematical number of
ancestors doubles with each generation. (Two parents, four grandparents,
eight great-grandparents, and so on.) You don't have to go back very far
in anthropological terms (well within historical time) before the value of
this expanding sequence exceeds the total human population of the Earth at
that time. So, logically, you HAVE to have convergence (inbreeding, if
you want to use emotionally loaded terms) somewhere along that line.
Since human interbreeding is nowhere near completely randomly distributed
across the planet, especially given the low level of population mobility
through the vast majority of recorded history, there is most likely a lot of
convergence. (How many people marry high school sweethearts, versus how
many people marry someone from the other side of the planet?) The whole
concept of 'race', after all, is nothing more or less than a very extended
family. So yes, we are families, and those families are inbred. Again,
the statement is technically accurate and operationally meaningless.

Glen


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